This invention relates to a vessel having a moon pool which is commonly used for laying pipe or laying fiber optic cable or for drilling wells under the sea. In typical ships, the moon pool is closed by using conventional hinged doors. These doors have various types of appendages which often snarl and snag on hydraulic cables and electrical connection lines as the pipe is being laid, or as divers use the moon pool. The present invention was developed to prevent the snagging of cables and lines while enabling the moon pool to be effectively used by eliminating the need for doors.
Numerous vessels have been build using moon pools. These vessels include cable-laying vessels, pipe laying vessels and drilling vessels. The moon pool is a round hole, open to the sea, located amidships into which the pipe or cable is fed. Ships with moon pools have been reported in various patents, see for example, U.S. Pat. Nos. 4,435,108, 5,013,186, which is directed towards a cable ship, U.S. Pat. 4,448,568 which is a marine facilities work station with a moon pool.
When the ship wants to leave a site, the moon pool is typically closed, with hatches. These hatches are often large door like objects which are hinged to the sides or bulkheads of the vessels. The hatches have pins and objects which protrude outwardly when not locked together. These outwardly producing members have caused snagging and trouble in the industry. The present invention was created to provide an easy to use device for sealing a moon pool so that the vessel can quickly get underway with the minimum of snagging of lines.
The present invention tends to resolve the aforementioned problems in the prior art, and it is one object of the prevent invention to provide a vessel which can be plugged with a buoyant moon pool plug without the need for hatches.
According to one feature of the present invention there is provided a ship including a moon pool plug which has (a) interior plates for strength, (b) means for receiving and expelling air and sea water for deballasting and positive buoyancy, (c) guide means to orient the plug while under water and while rising to the moon pool, and (d) hoisting means to lift the plug onto the deck of the vessel.
The invention relates to a vessel, comprising a moon pool positioned in the center of the vessel, a buoyant moon pool plug adapted to have controllable positive and negative buoyancy; with the plug comprising: a top; a cover; a bottom; a first angled side; a second angled side; a third angled side; a fourth angled side with the first plates disposed traversely across the bottom of said plug; and the second plates disposed perpendicular to the first plates across the bottom of said plug: a water valve for permitting sea water to egress from said plug; a air valve for permitting air to be pumped into said plug; guide means secured to the buoyant moon pool plug to guide said plug into the moon pool; and hoisting means secured to the plug to lift the plug into the desk of the vessel.
The invention also relates to a method for installing a buoyant moon pool plug in a moon pool of a vessel that comprises the steps of: securing a guide means to the plug; moving plug into the sea; submerging and deballasting plug in the sea by filling the plug with sea water; positioning the plug with respect to the vessel beneath the hull and the moon pool; orienting the plug with guide means, and expelling the sea water from the plug enabling the buoyant moon pool plug to have positive buoyancy and to rise into the moon pool of the vessel.
The above mentioned and other objects, features and advantages of the present invention will become more apparent by referring to the following description of one preferred embodiment of the invention made in conjunction with the accompanying drawings.